Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.79	13.410%	$132.4515	$132.45	$132.45	$132.50
Purchase #2	$240.78	10.358%	$265.72	$265.72	$265.70	$265.70
Purchase #3	$238.86	4.595%	$249.8356	$249.84	$249.85	$249.80
Purchase #4	$75.56	7.418%	$81.165	$81.17	$81.15	$81.20
Purchase #5	$89.72	9.735%	$98.4542	$98.45	$98.45	$98.50
Purchase #6	$67.38	6.589%	$71.8197	$71.82	$71.80	$71.80
Purchase #7	$99.56	12.443%	$111.9483	$111.95	$111.95	$111.90
7 purchase totals =	$928.65		$1,011.3943	$1,011.40	$1,011.35	$1,011.40